I don't have a problem with investing in the hood either, but you have to remember that the people who are going to rent your units there are mostly not the greatest people to deal with either. You will have lots of drama and have to understand how to stay out of it. Also as Mike said, there is a big difference between a low to no income neighborhood and a war zone, although I have to add, what one person see's as a war zone, another person who has worked or lived in that environment, may find it OK. Much of it is a matter of perception.
I use 2 rules when I am hunting for a deal. First is, will I feel comfortable letting my wife and young daughter work in this house without me and second, when it's vacant will I have to worry about someone breaking in and stealing all the wiring out it. I have been looking at an area of really cheap rentals, the area is bad, but do-able, but then I turn around and think about the house being vacant over night and how much it's going to cost me to replace the breaker box, wiring and damaged door and it just comes down to it's not worth the risk.
This is a white, low to no income neighborhood, where the tenants sit on the front porch all day and drink beer and smoke pot. I would feel comfortable in this neighborhood and get along well with them, because I grew up around these type of people. But these same people will turn around and steal from you just as fast as you turn your back and I wouldn't feel good with letting my wife help rehab a house down there.